Author:
Greenwood Paul L.,Slepetis Ramona M.,Bell Alan W.
Abstract
This study investigated associations between fetal and placental weights from
85 to 130 days gestation in 49 fetuses from 21 ewes of a prolific genotype
used as an experimental model of intrauterine growth retardation. The
proportion of variation in fetal weight explained by placental weight
increased from zero at 85 days to 91% (residual standard deviation
(RSD) = 260 g) at 130 days. Overall, stage of pregnancy plus placental
weight accounted for 96% of fetal weight variation (RSD = 212
g). Litter size and number of fetuses per uterine horn also influnced
individual fetal weights. Gestational age, litter size, placental weight per
ewe, and liveweight and condition score of ewes during early to mid gestation
(initial LW and CS) explained 99.5% of the variation in fetal weight
per ewe (RSD = 236 g). Most variation (86%) in placental weight
was explained by stage of pregnancy, litter size, number of placentomes, and
initial LW and CS (RSD = 53 g). Placental weight per ewe was influenced
by stage of pregancy, litter size and initial ewe LW and CS
(R 2 = 0.97; RSD =
89 g). The association of fetal and placental weights with initial ewe LW was
positive, and with initial CS was negative. The results show that in the
absence of overt nutritional restriction of pregnant ewes, fetal and placental
weights are tightly coupled during late gestation and ewe fatness during early
pregnancy is inversely related to placental and fetal weights. They
demonstrate that placental weight explains most of the variation in fetal
weight in the present intrauterine growth retardation model.
Subject
Developmental Biology,Endocrinology,Genetics,Molecular Biology,Animal Science and Zoology,Reproductive Medicine,Biotechnology
Cited by
56 articles.
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